Method and apparatus for wet winding coil assemblies for transformers



Aug- ,12, 1969 H. FORECKI 3,461,011

METHOD'AND APPARATUS FOR WET WINDING COIL ASSEMBLIES FOR TRANSFORMERS Filed Feb. 12, 1965 INVENTOR. HARRY FORECKI RONALD E. BARRY United States Patent Ofice 3,461,011 Patented Aug. 12, 1969 US. Cl. 156-171 Claims ABSTRACT OF THE DISCLOSURE A method and apparatus for winding a wire coated with a wet composition or substance onto an electrical assembly having an insulating barrier material, said composition penetrating the barrier material in the area of the Wire. The apparatus includes a flexible tubular member having a compressible seal at the inlet and a restricted orifice at the outlet and a reservoir of organic resinous composition connected to the tube to maintain the tube filled with the composition.

This invention relates to coil assemblies for transformers principally of the oil-immersed type and more particularly to a new apparatus and improved method of utilizing such apparatus for wet winding such coil assemblies.

As is well known, transformers of the type contemplated herein include coil and core assemblies that are made up of alternate layers of electrically conductive material and insulating barrier material, the latter of which must have mechanical properties that are capable of withstanding the thermal effects in operating such transformer when immersed in oil and also must combine with the transformer oil to produce the dielectric characteristic for the transformer. Any increase in the operating temperature of these transformers results in an adverse efiect on the tensile properties of the insulating barrier material used in the core and coil assemblies with corresponding effects on the dielectric characteristics of the transformer,

As pointed out in copending application Ser. No. 416,125, filed Dec. 4, 1964 now abandoned, the ability to retain tensile strength, of the insulating barrier material used in such coil assemblies can be upgraded by the addition of organic resinous substances, such as insulating varnish compositions with a corresponding enhancement of the dielectric characteristic of the transformer. These substances are known to have enhanced the mechanical properties of the insulating barrier material by the chemical modification of the cellulose molecules of the paper either by (1) reactions with the substances involving the replacement of the hydroxyl (OH) radicals of the cellulose molecules to provide fewer molecular sites for dehydration of the paper, or (2) by reactions of the substances with the chemical products of the paper upon subjection thereof to elevated temperatures during use of the coil assembly.

At the preent time, these substances are being added to the insulating barrier material by the paper manufacturer and supplied to the transformer manufacturer for incorporation into the coil assembly. Paper manufacturers have not found this to be a very profitable practice because of the increased cost of manufacture as well as the requirement for special equipment and separate production lines for making this special paper. The transformer manufacturer has also found this to be a costly practice because of the higher overhead costs of the paper manu facturer which are being passed on to him.

One of the primary objects of the present invention is to reduce the cost of fabrication of electrical conductor assemblies that have enhanced ability to retain tensile strength and at the same time maintain their dielectric characteristics.

Another object is to prvide a device for applying a substance to the electrically conductive material at'the time of its incorporation into the coil assembly to upgrade tensile strength and thereby maintain the dielectric characteristic of the coil assembly for an oil-immersed transformer,

Another object of the present invention is to provide an apparatus for applying a substance to the coil assembly for an oil-immersed transformer to upgrade the thermal stability of the dielectric and mechanical properties of such transformer which can be incorporated into the present coil winding practice without any significant change in the present winding technique.

Another object of the present invention is to provide an apparatus for applying an adhesive substance to the electrically conductive member of a coil assembly at the time of incorporation of the member into the assembly to bond the component parts of the assembly together.

Another object of the present invention is to provide a new and improved method of wet winding coil assemblies for oil-immersed transformers which improves the ability of the insulating barrier material to retain its tensile strength.

A further object of the present invention is to provide a wet winding apparatus which can be incorporated into the present method of dry winding coil assemblies for oilimmersed transformers which requires a minimum of maintenance and substantially no operating costs.

A still further object of the present invention is to provide a method for adhesively bonding the component parts of an electrical coil assembly together and to enhance the ability of the coil assembly to maintain its tensile and dielectric characteristics at the operating temperatures of the transformer.

The present invention overcomes these problems and accomplishes these objects by the-application of an organic resinous substance during the fabrication or winding of the coil assemblies; that is, at the time that the electrically conductive and insulating barrier material is wound into the coil assembly. As is well known, coil assemblies of this type are normally wound dry on rotating mandrels with layers of electrically conductive wire alternately wound on layers of insulating barrier material. The entire coil assembly is then dipped in an adhesive substance to bind the component parts together. It has been found that to enhance the ability of the insulating barrier material to retain its tensile strength it is only necessary to apply small amounts of the substance to the insulating barrier material in the areas where the greatest amount of heat is generated; that is, the areas adjacent the electrically conductive material. Thus, a cost savings can be achieved if theamount of the substance applied is limited to these areas only, as well as an enhancement of the dielectric characteristics of the transformer. This can be accomplished during the winding operation by applying the substance in liquid form to the electrically conductive wire only.

A further advantage which can be accomplished by the present invention is a cost savings in the fabrication of t 3 the-coil assembly. It has-been found that an adhesive material can be used as a carrier for the substance which will bond the component parts of the coil assembly together on curing. This eliminates the necessity of dipping the coil assembly after the winding operation.

Another advantage which can be attributed to the present invention is the enhancement of the dielectric characteristics of a transformer when fabricated with a wet wound coil. If pretreated barrier material is used or the coilis dipped in varnish, the solid additives in these materials tend to create pockets of such additive substance in the barrier material which prevents impregnation of the interstices of the paper by the liquid insulating material. When the bonding resin is carried on the wire, it will be supplied only to the areas of the barrier material adjacent to the wire. The remainder of the barrier material will be unaffected by the bonding resin, allowing for complete impregnation of the barrier material by the liquid insulating material.

The applicant has designed an apparatus for applying the organic resinous substance with an adhesive carrier to the wire which can be placed between the coil winding mandrel and the stand for the roll of wire which does not require any major change in the present dry winding arrangement. This apparatus comprises an elongate tubular member connected to a source of the resinous substance so that it will be completely filled with the resinous substance at all times. The electrically conductive wire is fed through a sealed inlet into the tubular member and is forced through the entire length of the tubular member until it passes through a restricted orifice at the outlet end of the tubular member. The free end of the wire is then wound on the mandrel and as the mandrel is rotated, the wire will be drawn through the tubular member. Since the tubular member is filled with the resinous substance, it will coat the outer surface of the wire completely. As the wire is wound onto the mandrel, the wire will still be wet so that the substance will readily adhere to the insulating barrier material. As pointed out above, the incorporation of this apparatus into the present arrangement for winding such coils has not affected the basic winding technique and has solved the above objections at substantially no increase in overall costs.

These and other objects, features and advantages of the present invention will become more readily apparent when the following detailed description is read in connection with the accompanying drawings, in which:

FIG. 1 is a schematic view of a coil winding apparatus.

FIG. 2 is an enlarged view in section of the apparatus for applying the liquid to the electrically conductive r material.

Referring more particularly to the drawing, a schematic view of a coil winding system is shown in FIG. 1. A coil assembly is shown being wound on a rotating mandrel 12 which is driven off any appropriate power source 14. A coil of electrically conductive wire 15 is mounted for free rotation on stand 16 and the free end of the wire 18 is normally wound on the mandrel. Rolls of insulating barrier material 20 are mounted on stand 22 on the other side of the mandrel and are selectively wound into the coil assembly as needed. The insulating barrier material and electrically conductive material are alternately wound into the coil assembly. The above winding arrangement is fairly standard in this industry and does not form any part of the present invention.

In order to wet wind the wire with a liquid substance applied to the electrically conductive wire during assembly, the end of wire 18 is first passed through the liquid applying apparatus 24 before it is wound on the mandrel. The liquid applying apparatus includes a fixed inlet fitting 44 secured to end 26 of a flexible tubing 25. An outlet fitting 46 is secured to end 28 of the tubular member and is free to move with the wire due to the flexibility of tube 25.

'- Referring to FIG. 2, it will be seen that inlet'fitting 44 provided on end 26 of the tubular member includes a central passage 48 which is connected to central passage 50 in the tubular member and a passage 53 for the admission of the substance. The open end of the fitting is closed by a cap 54 threadably secured to the fitting and has an aperture 56 provided in the center of the cap. Neoprene seals 58 are enclosed within the cap and have a central aperture 60 which is coaxial with passage 48 and aperture 56. When the cap is tightened onto the fitting, the neoprene seals will be squeezed or compressed into snug engagement with the end of the fitting and with the wire which has been inserted through apertures 56 and 60 and into passage 50. This prevents any of the substance within the tubular member from flowing out of the tubular member. A relief port may be provided in fitting 44 with an appropriate cap to allow for draining of the tubular member when not in use. The inlet fitting can be secured to any fixed structure such as stand 51 to support the inlet in a fixed position. i

The outlet fitting 46 is provided with a central passage 62 connected to a nozzle 64 having a restricted orifice 66 through which the wire passes. Passage 65 is provided to allow the substance to completely fill the passage. The size'of the orifice is chosen according to the size of the wire so that a predetermined amount of liquid is left on the wire as it leaves the tubular member. It is important to restrict the amount of the liquid substance left on the wire because of the possibility of any excess liquid being thrown off of the wire by centrifugal force as it is wound on the mandrel. A nylon (polymeric amide) or Teflon (tetrafluorethylene) nozzle should be used at the outlet and should be sized to limit the amount of material left on the wire as well as to prevent the substance from leaking from the tubular member.

A reservoir 30 of the organic resinous substance is positioned on stand 36 next to the apparatus at a point above the tubular member so that it can be gravity fed to the tubular member. A connecting tube 38 has one end connected to the bottom of the reservoir and the other end to passage 53 in fitting 44 at end 26 of the tubular member. A return tube 40 has one end connected to passage 55 in fitting 46 at end 28 of the tubular member and the other end to the top of the reservoir. Valves 42 and 43 are provided in tubes 38 and 40 to control the fiow of the substance to the tubular member. It will be apparent that when the valves are opened, the resinous substance will completely fill the tubular member and will rise in tube 40 to the level of the substance in the reservoir. This assures that the tubular member is completely-filled at all times.

As pointed out in copending application Ser. No. 416,- there are a number of substances which can be used to treat the paper or barrier material 20. Amine compounds, such as dicyandiamide, urea, diethylenetn'amine and ethylene diamine have been found to have excellent reaction properties with cellulose base insulating barrier material, such as Reigel kraft paper. Solid substances, Such as urea and dicyandiamide, are preferably supplied to the barrier material in the form of a solid suspension. The carrier for such suspension may be a varnish, such as P. D. George 521, sold under thattrade name by P. D. George Paint & Varnish Company, or a Butvarurea composition comprising three parts by weight of Butvar and one part by weight Resimene 883 solid (melamine resin) in an alcohol-toluene mixture. This carrier will act as an adhesive on curing and will bond the component parts of the assembly together.

The substance can be added to the carrier preferabl in the ratio of one part by weight substance to three parts by weight carrier solids., Preferably the weight ratio of substance additive, to carrier solids results in 1.5% substance based on the weight of the paper to which the substance carrier composition is added. The thickness of the quantity of the substance, with or without carrier, added to the barrier material can be controlled, as desired, and the feature of controlling the quantity of substance added as pointed out above is one of the advantages of using this apparatus.

It should also be noted that is within the ambit of this invention to precoat the electrically conductive material with the substance and an adhesive at the manufacturing point and to activate the prccoated adhesive by passing it through the apparatus prior to its application to the coil assembly.

As an example, an electrically conductive Wire with a conventional enamel coating and having a second coating containing the substance and a carrier such as shellac could be drawn through the apparatus which could be filled with a solvent, such as alcohol to activate the adhesive carrier.

Although only one embodiment of the present invention has been shown and described, it should be apparent that various changes and modifications can be made without departing from the scope of the appended claims.

What is claimed: 1. The method of wet winding a coil assembly com posed of electrically conductive material and insulating barrier material separately wound on a mandrel to form the coil assembly, comprising the steps of filling an elongate tubular member with a liquid substance which enhances the ability of the insulating barrier material to retain its tensile characteristics,

passing an electrically conductive member through said tubular member so that it is coated with said substance,

controlling the amount of substance that is coated on said conductive member as said conductive member leaves said tubular member,

winding layers of said coated conductive member while said substance is still wet, and

alternately winding layers of insulating barrier material on the mandrel between said layers of conductive members.

2. The method of wet winding and adhesively bonding layers of an electrically conductive member and an electrically insulating barrier material onto a mandrel to form an electrical assembly, comprising the steps of rotating the mandrel,

passing the electrically conductive member through an organic resinous substance prior to winding a layer of said member onto the mandrel to form the coil assembly, and

alternately winding layers of the barrier material and conductive member onto the mandrel, while the substance is still wet. 3. The method of wet winding a coil assembly for an oil-immersed transformer, said coil assembly having alternate layers of electrically conductive material and insulating barrier material, comprising the steps of precoating the electrically conductive material with a substance which enhances the ability of the insulating barier material to retain its tensile strength,

passing said precoated material through a tubular member filled with an activating solvent for said precoated substance,

winding said material with said activated substance onto the mandrel to form the coil assembly, and alternately winding layers of insulating barrier mate rial and conductive material on said mandrel.

4. An apparatus for coating a wire with a composition, said apparatus comprising a flexible tubular member,

a fixed inlet having a compressible seal to engage the wire at one end of said member,

an outlet at the other end of said member, said inlet and outlet being adapted to support the wire for movement through said member, and

means for maintaining said member filled with the composition.

5. An apparatus for coating a wire as the wire is being wound on a mandrel to form an electrical assembly having an insulating barrier material, said apparatus comprising a stand,

means on said stand for rotating the electrical assemy, a tube having a compressible inlet to sealingly engage said wire and an outlet having a restricted orifice,

an electrically conductive wire threaded through said inlet and outlet in said tube and wrapped around the barrier material on said rotating means,

and means for maintaining the tube filled with a composition to enhance the tensile strength of the barrier material, whereby said wire is wetted with the composition as the wire is wrapped on said rotating means and the composition will penetrate the barrier material around the wire.

6. Apparatus for the assembly of wire wound coils, comprising a mandrel on which the coil is wound,

a supply of sheet insulating barrier material,

a supply of wire, said sheet material and wire being alternately wound on said mandrel in layers,

and means for wetting the wire just prior to winding the wire on the barrier material with a liquid substance to enhance the tensile strength of the barrier material and bond the wire to the barrier material, whereby said substance will impregnate the barrier material in the area contacted by the wire.

7. An apparatus according to claim 6 wherein said wetting means includes a flexible tube.

8. An apparatus according to claim 7 including a compressible member in said tube to sealingly engage the wire, and

a restricted orifice in said tube to control the amount of the substance deposited on the wire.

9. The method of wet winding and adhesively bonding an electrically conductive wire to an electrically insulating barrier material in an electrical assembly comprising the steps of alternative winding layers of wire and barrier material on a mandrel to form the essembly, and

wetting the wire with a substance to adhesively bond the wire to the barrier material and to enhance the tensile strength of the barrier material prior to winding the wire on the mandrel,

and allowing the substance to penetrate the barrier material in the area of the wire.

10. The method of claim 9 including the step of controlling the amount of substance applied to the wire.

References Cited UNITED STATES PATENTS 762,111 6/1904 Apple 156-171 XR 2,016,900 10/1935 Humberstone 156-428 2,814,581 11/1957 Flynn 156-305 XR 2,561,462 7/1951 Compton et al. 156-171 XR 2,007,277 7/1935 Keyes 156-53 XR 2,952,240 9/1960 Abbott 118-405 PHILIP DIER, Primary 'Examiner US. Cl. X.R. 

